Image sensors are ubiquitous. They are widely used in digital still cameras, cellular phones, security cameras, as well as, medical, automobile, and other applications. The technology used to manufacture image sensors has continued to advance at a great pace. For example, the demands of higher resolution and lower power consumption have encouraged the further miniaturization and integration of these devices.
As with many semiconductor-based devices, such as image sensors, latch up is a concern for device performance and reliability. Latch up may occur for various reasons related to die layout, relative placement of n-wells, p-wells, highly doped regions, etc., and how those various areas become biased with respect to one another. While latch up is not a recent issue, the solutions that have long been viewed as industry standard may not always be amenable to further miniaturization of semiconductor devices, including image sensors.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.